Tattoos have been expressly prohibited in Islaam because of it changing the creation of Allaah, to the extent that the one who does it gains the curse of Allaah and His Rasool Sallallaahu `Alayhi Wa Sallam.

Hadhrat `Abdullaah Ibn Mas`ood Radhiallaahu `Anhu said: “Allaah has cursed those women who tattoo (others) and those who get themselves tattooed, and those who get their eyebrows plucked, and those who make gaps between their teeth for the sake of beauty, those who change the creation of Allaah.”

So news of that reached a woman from the tribe of Bani Asad who was called Umm Ya`qoob, so she came and said: “It has reached me about you that you have cursed such-and-such (women)?”

So he said: “And why should I not curse those whom Rasoolullaah Sallallaahu `Alayhi Wa Sallam has cursed, and those who are (mentioned) in the Book of Allaah (the Qur’aan)?”

She replied: “I have read what is between the two covers (i.e. the whole Qur’aan) and I did not find in it what you are saying.”

He said: “If you had read it then you had found it, did you not read: “Whatever the messenger gives you, grab hold of it, and whatever he prohibits you from, abandon it.” (Surah Hashr Aayah 7)?

So she went and looked, but she did not see anything which she had thought.

So he said: “If she was like that I would not live with her (I.e. rather I would have divorced her).” – Saheeh Al-Bukhaari.[i]

Hadhrat `Abdullaah Ibn Mas`ood Radhiallaahu `Anhu also said: “I heard Rasoolullaah Sallallaahu `Alayhi Wa Sallam curse those women who pluck their eyebrows, those who make gaps between their teeth (for the sake of beautification) and those who get tattooed, (because) they are those that change the creation of Allaah `Azza Wa Jall.” – Sunan An-Nasaa’ee. [ii]

Although these Ahaadeeth mention women, the prohibition actually applies to both men and women, but women were mentioned because these were things that women were mostly involved in.